There are three parts to using solar energy efficiently;
efficient collection or generation of energy
efficient storage and
efficient use to offset demand loads.

Of these three the missing link is typically the storage efficiency of the collected electrical or thermal energy from the sun. I am looking for input regarding projects using efficient long term storage that would empower collection of energy during the hot summer months and use during the winter months. A seasonal cycle rather than a daily cycle.

Specifically requesting any information on long term electrical starage and long term thermal storage of energy.

I was reading a magazine article on the bus this morning about Ground Source Heat Systems, incredibly popular in Scandinavia. It described how they sometimes used solar panels to replace some of the warmth extracted from the ground during the winter (I think). Even the ambient temperature of the ground can be a limited resource if all your neighbours are also using it!

GSHP's are probably the closest thing to what you describe, a heat source in Winter and a heat sink in Summer.

What do we do with CO2 emissions to mitigate the global environmental impacts?
CO2 Capture Technologies are currently too expensive.
Carbon Capture Technologies

It is imperative to protect the environment from manmade CO2 and conventional coal plants should not be constructed without carbon capture technologies. Before carbon dioxide (CO2) gas can be sequestered from power plants and other point sources, it must be captured as a relatively pure gas. Existing capture technologies, however, are not cost-effective when considered in the context of sequestering CO2 from power plants. Currently amine absorbers and cryogenic coolers are used to recover CO2 from combustion exhaust. The cost to capture the CO2 is currently $150.00 per ton or an electricity cost increase of 2.5 cents to 4 cents /kwh depending on the type of process. To make CO2 capture worthwhile it must have a value or other substantial contribution post capture and sequestration, that exceeds the cost recovery of current industrial uses.

To be successful, the techniques and practices to capture and sequester carbon must meet the following requirements:
• be effective and cost-competitive,
• provide stable, long term storage, and
• be environmentally benign.

Three capture technologies and four geologic storage mechanisms are envisaged. These are described and illustrated below:

Capture Technologies

Post-Combustion Scrubbing
Considered the first step towards large-scale capture, CO2 is removed from exhaust gas after combustion. This technology can be retrofitted to existing
equipment.

Pre-Combustion Decarbonization (Hydrogen)
Natural Gas is converted to hydrogen and CO2 in a reformer. The CO2 is compressed for storage and the hydrogen is mixed with air for combustion, emitting only nitrogen and water.

Oxyfuel
Oxygen is separated from air and then burned with hydrocarbons to produce an exhaust with a high concentration of CO2.

Carbon Sequestration

Geologic Storage
The schematic diagram below illustrates options for geologic storage. Note that some options provide additional energy and the potential to recover the cost of carbon capture.

Using present technology, estimates of sequestration costs are in the range of $100 to $300/ton of carbon emissions avoided. The goal of the program is to reduce the cost of carbon sequestration to $10 or less per net ton of carbon emissions avoided by 2015. Achieving this goal would save the U.S. trillions of dollars.

No doubt, we can achieve some cost reductions with improved process and technology but the capacity to turn sequestration of CO2 into profits and achieve direct recovery of the cost would be just as good and achieving both would be better.

The key to unlocking the solution to all such problems is embodied not only by what is prevented, in this case a compelling incentive, but more importantly by the more desirable future state that is empowered and the significant additional net value added.

Transition to alternative renewable energy power generation systems and a more desirable, economical and sustainable energy future requires a solution to the problem of energy storage.

We need the missing piece of the puzzle. Fossil fuel needs viable alternatives to replace it’s current role in our civilization. Supercritical CO2 sequestered in depleted oil & gas reservoir following advanced oil recovery processes can be used to store massive amounts of energy because of the energy embodied in the phase change of the CO2 gas to supercritical state. The cost and energy that is invested in the process is of course recoverable and it thereafter empowers unlimited deployment of solar photo-voltaic power plant, wind mill farms and small scale hydro. In the short term such a strategy empowers economic justification for carbon capture and sequestration.

I would like to discuss the invention with DOE and work with DOE to determine the feasibility of the idea. I am not affiliated with any University or National Laboratory. I have limited experience working with Federal agencies and would appreciate advice regarding how best to proceed.
I am an architect with considerable engineering experience. I appreciate your time and interest and would request a response from an individual with appropriate technical expertise regarding this concept. Please find below my contact information and a link to my web site.
Walker Architects
Terry L. Walker, AIA
21712 21st Ave. West
Brier, WA 98036
206-718-6782
terrylwalker@comcast.net

IntroductionContinued use of fossil fuel remains problematic in the context of global warming, the population explosion and rapid nuclear proliferation, given anticipated oil production shortfalls. These three parallel vectors drive the need for accelerated change in energy policy and technology. Circumstance mandates Energy alternatives, Energy Conservation and Energy Storage Systems.

Sequestration of carbon dioxide (CO2 ) is a critical component of the overall climate challenge. Tanks have been used by man to store CO2 for the last 100 years and suitable geologic formations for long-term carbon dioxide sequestration are now being studied. The technologies for CO2 subsurface injection are established.

Separating CO2 from the atmosphere or fossil fuels and preventing emission by capture and conversion into compounds or other permanent storage method is called carbon sequestration. There are three working types of carbon sequestration:

1. Geologic – piping CO2 from the source into extracted oil and gas fields; 2. Oceanographic – piping CO2 from the source to the bottom of the ocean; 3. Terrestrial – the long-term storage of carbon in organic matter (soil) or in trees.Tanks are small suitable working gas storage for CO2. For long-term sequestration, CO2 must be injected deep into a reservoir below the Earth’s surface, at a depth and pressure where CO2 is contained as a supercritical fluid, a state neither liquid nor gas that embodies properties of both. Supercritical CO2 is denser than CO2 gas and thus requires less storage volume. Supercritical CO2 is also easier to contain and has a higher solubility underground, which makes such large scale sequestration effective.

A massive expansion of the present sequestration technology is required before enough CO2 can be locked away to mitigate the rate of emission. Technical and nontechnical concerns remain to be addressed as well as the problems of time and expense. We need better solutions.

Energy storage is the storing of some form of energy that can be drawn upon at a later time to perform work. CO2 stored under pressure, in a tank or sequestered underground in a suitable geologic formation, is a reservoir of potential energy. There is hope to turn the cost burden of CO2 sequestration to our advantage and use it as energy storage to empower alternative renewable sources of energy to replace fossil fuels. Once captured and reservoir created, the CO2 needs to be closely monitored, maintained and secured for centuries to come.

Concept:My concept, is to “bottle surplus electricity and CO2 at the same time and in the same place. Earthquake and volcanic activity is not compatible with CO2 sequestration strategies. The central idea is to store electrical energy generated in summer for use in winter. Generated electrical energy and thermal energy are stored as liquid or supercritical CO2 in the form of pressure, temperature and energy embodied in the phase change of liquid or supercritical CO2. On demand that stored energy can be recovered from the temperature, pressure and phase change expansion as the working fluid converts instantaneously back to a gaseous state. That energy is used to drive engines and generate electrical power. The CO2 can be sequestered in underground vaults or contained in manmade tanks as a working fluid. An energy storage cycle applicable to large and small scale.

Declaration:I declare and have claimed as my intellectual property an innovative method that uses CO2 or other suitable substance with suitable properties to store energy for long periods of time for later use. This method would store power from; all renewable energy sources; hydro electric, solar photovoltaic, solar thermal, wind turbines, or any other source of electrical power used to drive the pumps & compressors and thereby store energy in the CO2 reservoir as potential energy for later regeneration as electrical energy. This new technology, process & method is an energy storage & power regeneration system. This submission describes a new way to develop and use both the existing energy generation infrastructure and new renewable alternatives to more efficiently combat climate change by reducing greenhouse gas emissions.

Invention:There has been invented a storage/power regeneration plant. Captured CO2 is first sequestered as a reservoir of liquid or supercritical CO2 in a geologic formation or in a pipe or a tank. The cycle begins when the reservoir is used to store additional energy. A compressor driven by surplus electrical power from any alternative or conventional energy source is used to inject CO2 , increasing reservoir pressure and recycling the CO2 in the system. The working fluid expands in the reservoir and absorbs additional pressure and heat. Liquid or supercritical CO2 is then pulled up an extraction well from the reservoir into any suitable engine type at supercritical pressure. Pressure, heat and flash vapor phase change reaction all occur as the embodied energy is released creating an explosion which drives the engine to efficiently operate and mechanically regenerate electrical power. The CO2 is captured in a suitably large low pressure chamber then re-compressed in the energy input phase and returned to storage in the reservoir as liquid or supercritical CO2. The storage/power regeneration plant may be combined with large central-station power plants or scaled to fit small residential scale power plants.

• Affordable; sequestered CO2 is part of the global climate change solution, it is an economic imperative to put CO2 to work once you have it bottled up.• Providing long term energy storage a new link in the energy delivery chain.• New infrastructure backbone, raising the value of renewable energy to the market.• Securing and assuring the nation’s electricity infrastructure and our critical global assets.• Optimizing productivity of fossil fuel generation.• Adaptable to any location, with either natural or manmade underground vaults or tanks.• Feasible for large (>500 MW) to small of grid residential scale applications.• Simple concept; three operation modes: Energy Charging, Energy Storage and Electric Power Regeneration.• Needed for peak shaving and power smoothing.• Efficient use of surplus electrical power generated & otherwise lost.• Clean; fully encapsulated no combustion by-products.• Frugal, uses otherwise wasted potential to create energy storage and regeneration and transmit energy using existing infrastructure.Applications for the Proposed CO2 Energy Storage/Power Regeneration System:

• Arbitrage, storing surplus power and moving low cost power into higher price markets. Empowers a risk-free profit. Power profile fitting; supplies the demand for additional power for energy customers at peak demand hours.• Power redundancy and quality- voltage regulation, black start, frequency control and emergency power.• As an accumulator my invention converts renewable reverse metered energy into scheduled power available for delivery.• Facilitates large scale power generation plants that must shunt power.• Justifies CO2 sequestration as necessary renewable energy storage. Applicable to:1. Rooftop Solar Power Large scale concentrating solar power plants2. Wind Farms3. Small & Large scale hydro power4. Tidal and Wave powerAbstract:

There has been invented a generally applicable method and energy cycle for storing power in summer for use in winter, consisting of an underground reservoir that is created by pumping liquid or supercritical carbon dioxide or other suitable fluids hereafter called the working fluid, through an injection well into a suitable geologic formation such as a depleted natural gas or oil well or other natural formation or a suitable manmade structure. For this application locations in seismically active areas where earthquakes and volcanic activity is common are not suitable locations. The working fluid is then allowed to heat up and absorb the ambient geothermal energy and expand. Surplus (input) electrical energy from conventional or renewable energy power plant(s) is thereafter used to further pressurize the working fluid. Small scale applications may be constructed using lower pressure and temperatures ranges for example with liquid carbon dioxide as the working fluid. Larger application may use supercritical carbon dioxide as the working fluid using much greater pressures and temperature ranges.

A fully encapsulated closed-system power plant is then constructed that operates and is maintained at suitable high pressure by application of (input) electrical power and uses the working fluid in a cycle to drive pressure-type gas turbine(s) and associated generator(s) for the purpose of regenerating the output electricity, from which process the exhaust, now in a gaseous state and at a reduced pressure and temperature, is passed through heat-recovery and into the low pressure chamber(s). The gas is pulled by compressor(s) from the low pressure chamber compressed and condensed back into a liquid or super-critical state, by using the surplus (input) electrical energy and known and established industrial processes. The compression may involve multiple stages and is hereafter referred to as the compressor train, which includes heat related technologies.

The working fluid is now recycled again and again in a continuous cycle scaled in general to store energy in summer for use in winter. In a liquid or supercritical state the working fluid is moved through heat exchangers into the injection well that extends down into the reservoir contained by a suitable geologic formation, such as a natural subterranean cavity or a manmade structure. Within this subterranean containment the working fluid is used to store the energy of surplus electrical power from renewable or conventional electric power sources. In this part of the cycle the working fluid also absorbs additional pressure and also absorbs additional heat energy, such that the working fluid achieves higher super-critical parameters having elevated super-critical temperature and pressure.

When a demand for additional electrical power exists the working fluid is channeled upwardly from the subterranean reservoir through extraction well(s) designed to withstand elevated super-critical temperatures and pressures, the impurities from subterranean gas, water, or minerals and other solids are filtered and separated by known industrial methods from the working fluid prior to entering the turbine(s) inlet.

Said turbine(s) is designed to fit local conditions to extract the maximum electrical power generation from the working fluid and may where warranted include heat exchanger(s) and multiple energy conversion stages which will be hereafter referred to as the turbine/generator train. Heat recovery technologies will be used to enhance efficiency. The energy embodied in the working fluid by the temperature, pressure and the phase change from supercritical to gaseous form is converted to mechanical energy by the turbine(s) portion of the train and used to drive associated generator(s) in the turbine/generator train, with maximum possible efficiency for the local condition. The resulting electrical power is then conditioned and transmitted by existing conventional means in response to the demand load. Multiple extraction wells are preferable in large power storage applications.

Atmospheric thermal pollution and carbon emissions are prevented by heat recovery and complete encapsulation of the working fluids and gas. The invention uses the captured carbon dioxide that fossil fuel plants should capture and sequester, to reduce emissions that contribute to the global warming trend. Alternative energy systems such as wind and solar power generation need long term energy storage to offset intermittent or seasonal peaks and valleys associated with energy collection and production.

About CO2:See the CO2 & Steam Enthalpy Diagrams and compare.gas CO2 standard temperature and pressure. It has no liquid state at pressures below 5.1 atm. CO2, is an acidic oxide.

solid CO2 sublimates directly to solid below −78.51° C (-109.3° F).liquid CO2 at pressures above 5.1 atm. Supercritical carbon dioxide exists above its critical temperature (31.1°C) and critical pressure (73 atm.) in a fluid state. It is a supercritical fluid which has the properties of both gas and liquid. If the temperature and pressure are both increased from STP to be at or above the critical point for carbon dioxide it behaves as a supercritical fluid expanding to fill its container like a gas but with a density like that of a liquid. Energy potential of CO2 is superior to steam in this application.